It probably is a bad cap, though probably not either of the two big ones, or
you would have measured less DC on one than the other. A scope would be
useful. You could see big ripple, if any, on a cap where there shouldn't be
much. That's my suggestion. A bad cap, maybe 47uf to 470 uf, in a regulated
power supply area.

Mark Z.


"D MARSHALL" wrote in message
...
are the power supply caps ok?
try replaceing them.

"chris C" wrote in message
...

My Marantz SR-50 has developed a 50Hz hum thru both channels. It
started as a fairly quiet hum and has gotten worse over time. The
unit still works otherwise.

Looking inside I can see that a few components in the power amp stage
have obviously become quite hot at some stage. There is a brown
discoloration on the PC board underneath two pairs of small transistors
(Q701, 702, 703 & 704). These transistors become quite hot to touch
even when the amp is not loaded.

D810 (zener I think) on the power supply has also been quite hot at
some time (dark brown colour on PCB)

My multimeter gives a reading of 39V across both of the 4700uF power
supply caps.

Any help greatly appreciated.


--
chris C